docs: def role_instance(self, value):
          """The role_instance property.
          
          Args:
              value (string). the property value.
          """
          if value == self._defaults['ai.cloud.roleInstance'] and 'ai.cloud.roleInstance' in self._values:
              del self._values['ai.cloud.roleInstance']
          else:
              self._values['ai.cloud.roleInstance'] = value